Two-stage nozzle area control



Jan. 9, 1962 F. P. EVANS Two-STAGE NozzLE AREA CONTROL 2 Sheets-Sheet 1 Filed March 27, 1959 ATTORN EY Jan. 9, 1962 F. P. EVANS 3,015,935

Two-STAGE NozzLE AREA CONTROL Filed March 27, 1959 2 sheets-sheet 2 FIG--2 -7'0 f2 $5465 nera/170@ BY ATTORNEY United States Patent Ofhee 3,015,935 Patented Jan. 9, 1962 3,015,935 TWO-STAGE NOZZLE AREA CONTROL Frederick P. Evans, West Hartford, Conn., assigner to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Mar. 27, 1959, Ser. No. 802,468 11 Claims. (Cl. 60-35.6)

This invention relates to variable Larea nozzles such as for turbojet engines and more particularly toa two-stage automatic hydraulic control therefor.

ln turbojet engines having afterburners and nozzle area controls it is important that the area of the exhaust nozzle bear a predetermined relationship to certain operating conditions of the power plant. Thus, `for example, withou-t afterburning the nozzle area should be at a When the afterburner is to be lighted, the area of the nozzle is required to be opened a predetermined amount or enlarged a predetermined amount when ignition of the afterburner fuel flow is to take place. Following this as a result of certain engine operating conditions, it is desired to have the exhaust nozzle fully opened to some predetermined maximum. The initial opening and the nal opening of the exhaust lnozzle area must be done rapidly.

Itis therefore -a primary object of thi-s invention to provide a control system which provides for the attainment of the aforementioned nozzle area operation with a minimum of mechanism and a maximum of reliability.

It is a further object of this invention to provide a control system including la hydraulically operated control valve which responds to one engine operating condition such as compressor discharge pressure to signal the valve toward movement in one direction to provide one desired position of the nozzle area varying mechanism.

It is ya further object of this invention to provide for another condition of operation f the nozzle area control valve in response to a predetermined ratio of two engine operating variables-as, for example, the compressor discharge pressure and the fuel pressure in the fuel injection v manifold for the afterburner.

It is a still further object of this invention to provide a nozzle area control valve having a hydraulic latching mechanism.

These and other objects of this invention will become readily apparent from the following detailed description of the drawings in which:

FIG. lV is aschem-atic illustration in partial cross section showing arturbojet engine having a variable area nozzle and a control system therefor according to this invention;

FIG. 2 is =a cross-sectional illustration in partial schematic illustrating the two-stage nozzle yarea control mechauism',

FIGS. 3 and 4 are cross-sectional illustrations of a portion of the control mechanism of FIG. 2 illustrating the control spool valve in two different operating conditions; and

FIG. Sis an enlarged cross-sectional illustration of a typical two-stage nozzle yarea actuator.

Referring tof FIG. 1 a typical turbojet engine is generally indicated at as having a compressor 12, a combustion section 14 anda turbine 16 which drives the compressor. Downstream of the turbine an elongated duct section 18 is provided for afterburning operation. The exhaust gases from the afterburner section 18 are ejected through an exhaust nozzle 20 whose 'area may be varied by one or more movable eyelids or flaps 22.

Y The eyelids 22 are intended to be positioned to enlarge the area of the exhaust nozzle 20 as certain operating conditions yare attained during ignition and subsequent operation of the afterburner.

Fuel maybe supplied lfrom a suitable source of pressure to the line 30V to an on-oif valve 32 leading to an afterburner control 34. The afterburner control is shown here schematically but may be of the type more clearly described and shown in patent `application Serial No. 623,620 filed November 2l, 1956, by Thomas P. Farkas, now Patent No. 2,988,875. rl`he afterburner control 34 of course may sense a number of variables of power plant operation to provide the `desired fuel metering. Once the -afterburner control is on, the line 36 will be filled as will the line 38 leading to the control 40 and the line 42 leading to the afterburner fuel manifold 44. It will be apparent that the pressure existing in the afterburner fuel manifold 44 will be substantially the same as that existing in the lines 42 `and 3S as Well as the lines leading from the line 38 to the control valve 40.

Generally lthe control 49 will sense compressor discharge pressure via the line 48 and fuel manifold pressure via the line 3S to thereby control the pressure in the first and second stage lines 50 and 52, respectively, leading to the nozzle area actuators 54. The actuators 54 are intended to move the eyelids or flaps 22 to two different` positions depending on certain operating conditions to be described hereinafter.

Referring to FG. 2 the control valve 40 is illustrated in more detail. The control valve '40 comprises an outer casing tlwhich encloses a spool-type valve 62 having an upper land 64 and a lower land 66. The spool valve 62 includes a depending rod 63 which is adapted for limited engagement by the leftJhland side of a beam 72 which is pivoted through a pressure-tight connection `at 74. The right-hand end of the beam 72 includes a pin 76 connested to a link 78 which is controlled in its vertical motion by a bellows 80 and a servo piston S2. The righthand end of beam 72 is movable downwardly in response to the pressure level inside the bellows Sil-in other words, the level of the compressor discharge pressure being fed internally of the bellows Silvia the line 48. Secondly, the right-hand end of beam 72 is movable in an upward Idirection When a predetermined ratio exists between the pressure in the bellows 80 and the afterburner fuel manifold pressure which is directed to the chamber S6 at the bottom of the piston 82. Thus, the left-hand end of the beam 72 will first be moved upwardly when some predetermined compressor discharge pressure is reached and secondly in -a downward direction when some predetermined ratio of compressor discharge pressure and afterburner fuel manifold pressure is reached. These -two conditions of power plant opera-tion lhave some preselected values -for any particular engine to insure proper opening of the exhaust nozzle area dur-ing afterburner starting and afterburner continued operation.

The spool valve 62 is dependent upon its operative positions primarily by the variable orifices 90, 92, and 94. The valve face 67 controls the area of the orifice 90 While the upper side of the left-hand end of the beam 72'controls the orifice 92 While the lower side of the left-hand end of the beam A72 controls the area of the orifice 94. The sequence of operation of the control 40 and its spool valve 62 is as follows. First of all, the valve 62 will not even begin to operate until the afterburner control 34 of FIG. l is in an on position and fuel is flowing to the line 36 and the line 3S clearly shown in FIG. 2. When pressure has reached some predetermined level in line 38, this pressure will be transmitted to a line passing Compressor discharge pressure is conducted as a signal to -bellows S through line 4S. When compressor discharge pressure reaches a value, for example, 100 p.s.i.g., the bellows 80 will begin to move the right-hand end of b eatn V72 downwardly and the left-hand end of the beam 7,2 in an upward direction. This 100 p.s'.i.g. value necessary for actuation depends upon the adjustment of spring 112V. VThis causes the left-hand end of beam 72 to move the steam 68 in an upward direction a very slight amount. When the valve 62 and the land 66 have moved up only a Vfew thousandths (about .006), the pressure in the chamber 104 will begin to fall oli because it will be draining through the orifice 90 through the passage 116 downwardly through chamber 118 to the drain 120. As the valveland 66 moves upwardly, the pressure in 104 will continue to drop until the upward force exerted by the beam 72 will be just counteracting the force of the spring 1,12. When the left-hand end of beam 72 has moved up far` enough, it will then be restricting flow from the chamber 116 through the variable orifice 92. This in turn builds up the pressure in both passage 116 and the annulusV 104 whereby the valve 62 will move upwardly at a fairly rapid rate. The farther the valve moves upwardly, the more the oriiice 92 is closed such that there is a gain 'in the servo action moving the valve instantaneously in an upward direction.

This instantaneous action or"V the valve could be used as a positive fast control Without any other appurtenances if a single stage actuator were desired. However, it is desired to latch the valve in a iirst stage position when it has reached arpredetermin'ed upward movement. Thus,

' when the valve land 66 moves upwardlyV sufficiently to open the bypass passage 124 leading into the left-hand end of valve casing, full pressure will be applied to the lower side of the land V66. This will tend to move the valve land' upwardly even more until the passage 126 on the right-hand side of the valve casing is open.

This position of the valve land 66 is more clearly shown in FIG. `3. Under this condition the line 126 will drain the pressure from the lower side of the lvalve land 66 just suilciently until an equilibrium point is reached.

Under the equilibrium condition the valve 66 will remain e hydraulically latched in ythis intermediate upward position.

' 'Still referring to FIG. 3 with the valve 62 in the position shown, the land 64 at the upper end of the valve will have opened the line 50 leading to the iirst stage actuator such that high pressure from the line S on the lefthandside of the valve will be led directly to the line 50 to the lirst stage actuator to position the nozzle area varying mechanism to Vthe desired more open position. Thus, the nozzle -area is triggered or positioned so that ignition can be initiated or'some other sequence of aftenburner operation can be set inY operation.

It should be noted that with the valve 62 in the latched position'shown in PIG. 3, the left-hand end of the beam 72 (FIG. 2)" can now be moved downwardly out ofengagement with the steam 68 and opening the 'area 92 and the valve willV remain in its intermediate upper position, because the combined flow through restrictions 102 and V124 is su'icient to sustain pressureon the face 67 adequate to support the valve against the spring, even with areas 92 and 94in their maximum open conditions.

' yi'Referringagain to FIG. 2 when the compressor dischargev pressure in the bellows 80l and the afterburner Vfuel krmanifold pressure in the chamber 86 reach a prei determined ratio, the control rod 73 connected to the bellows 80 and the piston 82 will-be moved upwardly such that the left-hand end of the beam 72 will be moved downwardly thereby reducing the area of the orilice 94. It should be noted that the orilice 94 leads to a drain line `120. Therefore, closing of the orifice 94 will prevent flow of duid from either passage 116 or passage 126 to drain thereby building up the pressure in these passages and in the region on the lower side of the valve land 66. This build-up of pressure will immediately snap the valve,

62. to its full up position to the position shown in FIG. 4.

Under these conditions both the first and second stage actuator lines 50 and 52 are open to high pressure ow leading into the line 108 V011 the left-hand side of the valve control housing. Under these conditions the valve 62 will remain in its maximum up position against the stop 130 until the afterburner Vfuel controlV shut off.

. Under such a condition the pressure in the chamber below the valve face 67 drops off such that the spring 1712 can move the spool valve 62 downward; thus, the entire valve will drop to its maximum down position as shown in FIG.

The two-stage actuator may take any suitable form but one embodiment is shown in FIG. 5. Thus, the first stageV line 50 can be connected to the right-hand side of the cylinder 140 there-by acting on the right-hand side 142 of piston 144to the full left position. When the piston rod 146 is in its full right-hand position, its actuating piston 148 will be carried along by the piston 144. Subsequently, when the second stage actuator is energized, high pressure fluid through line 52 will pass through the orifice 150 thereby acting on the left-hand side of piston 148 moving it further tothe left as shown in FIG. 5. Thus,` the rod 146 will be moved fully to the left such that the eyelids 22 shown in FIG. 1 will be fully open. Suitable stops 1,60 and l162 are provided on the rightand left-hand sides of the piston 148 and a further stop 164 on the left-hand side of the piston 144 to limit the movement of the respective pi-stons.

The proper ratio of manifold pressure to compressor discharge pressure will cause immediate signals to lines 50 and 52 simultaneously whether or not the compressor discharge pressure had previously reached the 100 p.s.i.'g. first step pressure. This override feature insures proper area for afterburner light-on even at high altitudes where it has not been previously necessary to jog the eyelids open a little due to compressor discharge pressure exceeding 100 p.s.i.g. i'

When the high pressure lines 50 and 52 for the first and second stage actuators are connected back'to drain through the line 107, the larger exposedl areas of the left side of the pistons 144 and 148 will Vcause the rod 146 to be movedY to its" full righthand position thereby moving the AsV a result of this invention, it will be apparent that a very simple, hghly effective, fast operating, and highly reliable control mechanism has been provided to condition the area varying mechanism of an exhaust nozzle for suitable operating'conditions during ignition and continued operation of an afterburner.

' Although one embodiment ofV this invention has been illustrated and described herein, it' will beapparent that various changes may be madev in the construction and arrangement of the various parts without departing from the scope of the novel concept. Y' l What it is desired by Letters Patent is: Y

l.. A control for an afterburner'of a turbine type power plant including a variablef area nozzle, a fuel control for feeding fuel to the afterburner including a fuel metering control, means for controlling said variable area nozzle comprising a control valve actuated by the pressure of said Vfueland a actuator means "controlled by said control valve, said control valve including a main `control land, said actuator means vvarying the" area of said nozzle, means responsive toa first power plant variable indicative of power plant output for positioning the said control valve by saidv servo pressure for movingvsaid actuator means to a rst predetermined position, and means responsive to the ratio of said power plant variable and Va function of a second power plant variable for further positioning said control valve to move said actuator' means to a second predetermined position. Y y i' 2. A control for yan afterburner of a turbine type power plant including a variable area4k nozzle, a fuel control forfeeding fuel to theafter'bl'lrn;er` including ai fuel regulator, means for controlling said variable area v nozzle comprising a control valve actuated by the pressure of said fuel, actuator means controlled by said control valve, said control valve including a main control land, said actuator means varying the area of said nozzle, means responsive to a power plant pressure indicative of power plant output for controlling the position of said control valve by said fuel pressure for moving said actuator means in a first predetermined position, means responsive to the ratio of said power plant pressure and a function of operation of the afterburner for further positioning said control valve to move a second predetermined position, and means for deactuating said actuating means.

3. A control for an afterburner of a turbine type power plant including a variable area nozzle, a fuel control for feeding fuel to the afterburner including an onoff control, means for sensing the pressure of the fuel when said fuel control is on, comprising a control valve adapted to be moved by said fuel pressure, actuator means controlled by said control valve, said control valve including a main control land, said actuator means varying the area of said nozzle, means responsive to a gas pressure indicative of power plant output for positioning said control valve by said fuel pressure for moving said nozzles to a rst predetermined position, means responsive to the ratio of said gas pressure and a function of said fuel pressure for further positioning said control valve for moving said nozzles to a second predetermined position, and means responsive to said fuel pressure being shut off for deactuating said actuating means.

4. In a turbine power plant having a burner, a compressor, an afterburner and an exhaust nozzle downstream of the afterburner, means for varying an operative variable of said power plant including first and second actuator means, a control valve for controlling said varying means including first and second control ports for said first and second actuator means respectively, a source of fluid under pressure, a Ivalve spool including a iirst passage and a control land for sequentially connecting said source to said actuators, a hydraulic servo surface for moving said spool, a second passage leading from said source to said servo surface, a first variable area orifice varied by motion of said spool for regulating the pressure acting on said servo surface, means responsive to a iirst variable of power plant operation for selectively varying the area of said first orifice to move said spool a predetermined distance to connect said first passage with said source, means connecting said source and the downstream side of said first orifice for bypassing said orifice when said spool moves said predetermined distance, control means responsive to a predetermined ratio of said rst variable and a function of another variable of power plant operation, and a second orifice downstream of said first orifice and said bypass, said second orifice being connected to a low pressure and being controlled by said control means for further varying the pressure on said servo surface to move said spool to also connect said second passage with said source.

5. ln a turbine power plant having a burner, a compressor, an afterburner and an exhaust nozzle downstream of the afterburner, means for varying the area of said nozzle including first and second actuator means, means for injecting fuel into said afterburner including a control therefor, a control valve for controlling said area varying means including first and second control ports for said rst and second actuators respectively, a source of uid under pressure, a valve spool including a rst passage and a control land for sequentially connecting said source to said actuators, a hydraulic servo surface on said spool for moving said spool, a second passage leading from said source to said servo surface, a first variable area orifice varied by motion of said spool for regulating the pressure acting on said servo surface, a second variable area orifice in series with said first orifice for further regusive to a pressure in lating the pressure on said servo surface, means responthe power plant indicative of power output for selectively varying the area of said first and second orifices to move said spool a predetermined distance to connect said first passage with said source, means connecting said source and. the downstream side of said second orifice for bypassingsaid orifices when said spool moves said predetermined distance, control means responsive to a predetermined relationship of said power plant pressure and a' function of the fuel pressure supplied by said afterburner fuel control, and a third orifice downstream of said second orifice and controlled by said control means for further varying the pressure on said servo surface to move said spool to also connect said second passage with said source.

6. In a turbine power plant Vhaving a burner, a compressor, an afterburner and an exhaust nozzle downstream of the afterburner, means for varying the area of said nozzle including first and second actuator means, means for injecting fuel into said afterburner including a control therefor, means for placing said control in an on and oif position, a control valve 4for controlling said area varying means including first and second control ports for said first and second actuators respectively, a source of fluid under pressure, a valve spool including a lfirst passage and a control land for sequentially connecting said source to said actuators, a hydraulic servo surface on said spool for moving said spool, a second passage leading from said source to said servo surface, a first varia-ble area orifice varied by motion of said spool for regulating the pressure acting on said servo surface, a second variable area orifice in series with said first orifice for further regulating the pressure on said servo surface, means responsive to a gas pressure in the power plant for selectively varying the area of said first and second orifices t0 move said spool a predetermined distance to connect said first passage with said source, means connecting said source and the downstream side of said second orifice for bypassing said orifices when said spool moves said predetermined distance, control means responsive to a predetermined relationship of said gas pressure and a function of the fuel pressure supplied fby said afterburner fuel control, a third orifice downstream of said second orifice and controlled by said control means for further varying the pressure on said servo surface to move said spool to also connect said second passage with said source, and means responsive to the placing of said afterburner fuel control in an off position for moving said spool to a position to disconnect said first and second passages from said source.

7. A servo control device including a source of operating fluid lunder pressure, a control valve receiving fluid from said source, main actuator means controlled by said control valve, said control valve including a control land for directing fluid to said main actuator means, hydraulic means for moving said valve to control said actuator means, means responsive to a rst variable pressure means `for controlling said hydraulic means, said rst variable pressure responsive means providing a first signal, for

positioning the actuator to a irst position, a second variable pressure means lfor producing a second signal, and means responsive to a predetermined ratio of said rst signal and said second signal for positioning said actuator means to a second predetermined position.

8. A servo control device including a source of operating iuid under pressure, a control valve receiving fluid from said source, a main actuator means controlled by said control valve, said control valve having an axis, and including a control land for directing iluid to said main actuator means, a first passage between said land and said actuator means, hydraulic means for moving said valve to control said actuator means, means responsive to a rst variable for controlling said hydraulic means including a first variable area orice, a secondV variable, means responsive to a predetermined ratio of said rst emessa Variable and second variable comprising said operating uid under pressure forfurtherr'controlling said` actuator riieans including a second variable area orifice in senes With said first orifice, control land being corn-rolledv by vsaidi'sec'zon'd orifice, Va, second passage for directing ing fluid underV pressure, lay control valve receiving' fluid from said source, said VV'valve being movable along an axis, actuator means controlled by said valve, a pair of'separate passages connected between said valve and said actuator meansgvsaid' passages connecting" to said valve at points spaced along said axis, saidV control valve including a land for connecting in sequence said source with one, then yboth, of said passages, hydraulic means for moving sai-d valve to each of its sequential positions, said hydraulic means comprising a pair of variable orifices in series, and a hydraulic latch `for holding said land in a positionl between said spaced points comprising a variable bypass Yorifice connecting the upstream side of one of said pair of orifices with the upstream side of the other of said pairv of. orices.

10. A servo system having a control valve including a signal input lever, an actuator operatively connected to the control valve for sequential operation in accordance with the position of said signal input lever, said control valve comprising a housing defining a chamber, a movable valve spool disposed in the ychamber including a control'surface foirned on one end thereof, a spring acting on the opposite end of the valve spool for urging the valve in one direction, uid conducting passages foradi face mitna-uidrintqths chambei'r toast ou the Contrgl Sursansfgr'varvns thelpressur '0fY ,said Huid. inddv ing a pair -f serially connected variable-area orifices, the area of one of `svaid; orifices beinglvaried 5by the control Surface widths aradf. thfctherbc ,being varied by the'input. signal lever, the areaof said orices yfunctioning to vary ,the pressure of the fluidaeting on the control surface, meansr responsive ltcfaflirst signallfor positioning the rriontrol lever in 'one position, means responsive'to a SClO'nd signal 'fsf pbsitiomfng the Control lever ih a Second. position, whereby the'lirst ofsaid positions adjusts'the pressurefin said chamber tojmove y'said spool a predetermineddistancey in afspringl opposingv direction and the second ofsaidY positions adjusts the pressure in ysaid chamberto move, said spool a second predetermined distance in a spring opposing'directiol't'V nl1'. A servo system as delnedfin claim 10 including a Y valve stern projecting lfrom said valve s against vsaid sigt'ialy input lever.

Aoovl and abutting Vielferences Cited in the tile of this patent UNITED, STfIES VIKL'XfE/NTS 2,689,585 Bresfu' sept 21, 1954 2l,'/'8()',5 4y Coar etal. Feb. 5, 1957 2,893,944 Kroon V Y Aug. 27, 1957 Y FOREIGN PATENTS 1,107,141 France Aug` 3, 1955 749,745 Great Britain May `30, 1956 @Tues REFERENCES Aviation Age, Jet Engine Control Uses Pneumatic Parametes by Reed, vol. 275, No. Y5,Y 'pages r62-64, 69-71. 

